1. Field of the Invention
The present invention relates generally to spindle assemblies for self-propelled vehicles, and particularly to spindle assemblies having a coupling for disconnecting the spindle from a drive motor to provide a free-wheeling mode.
2. Description of the Related Art
A conventional spindle assembly 10 for self-propelled vehicles is illustrated in FIGS. 1 and 2. The conventional spindle assembly 10 provides a bearing and hydraulic motor disconnect package for use in the towable equipment market. It allows an equipment operator to do two primary functions:                1. Tow a vehicle from one job site to another when the spindle assembly is in the “disconnected” or “free-wheeling” mode; and        2. Once at a job site, to engage the vehicle's self-propelling drive system by means of a movable splined shaft connecting a hydraulic motor to the equipment's wheels.        
Typically, two spindle assemblies are used on vehicles, but some vehicles have only one. Major components of the conventional spindle assembly are shown in FIGS. 1 and 2 and include: a housing 11, a spindle 12, a wheel hub 13, a disconnect shaft 14, bearings 15, and a coupling 16.
The housing 11 contains the bearings 15 and spindle 12. The spindle 12 is splined in the center to allow for the connecting and disconnecting of the spindle assembly 10 from the hydraulic motor (not shown), as well as mounting of the wheel hub 13 where the vehicle's tire rim will attach. The disconnect shaft 14 is also splined and slides between the spindle 12 and the coupling 16 depending on which mode (connected or disconnected) the equipment operator requires. Pulling the shaft 14 out disengages the unit and places it in free-wheeling mode. A positive lock-out is included to assure the shaft 14 will not engage the coupling 16 while the vehicle is being towed. When the shaft 14 is allowed to engage into the coupling 16, the unit is placed in connected mode, and the vehicle can be moved on a job site with its own power. The conventional spindle assembly 10 allows for the mounting of the hydraulic motor directly to the housing 11 where the splined drive shaft on the motor will engage into the coupling 16 thus providing power to the wheels of the vehicle.
The hydraulic motor shaft is directly engaged into the coupling 16. This arrangement relies solely on the motor and hydraulic drive system for performance of the vehicle and smoothness of operation around the job site. However, in certain cases, optimal performance cannot be achieved with the motor based on the design of the hydraulic system or because of limitations with the hydraulic motor.
In the conventional spindle assembly 10, equipment operators must manually disengage the disconnect shaft 14 on each wheel with a handle 17 located in the center of the wheel. This handle 17 is located on the outboard side of the vehicle. While no fault of the design, operators often neglect to disengage the handle 17 when leaving a job site. This causes the torque from the vehicle's wheels to be transferred back from the road through the spindle 12 and into the hydraulic motor. The result often leads to damage occurring to the internal splines on the coupling 16, disconnect shaft 14 and/or spindle 12, as well as damage to the hydraulic motor. The conventional design does not allow for an efficient way to disconnect the spindle assembly 10 with the disconnect handle 17 in the existing location because anything that is added will greatly complicate tire changes if a flat occurs. Any change to the design will only add length to the disconnect handle 17, and that would lead to damage if the vehicle comes in close contact with another object when clearances at a job site are an issue.
There is a need in the industry for an improved spindle assembly having a disconnect feature for use with self-propelled vehicles to provide a free-wheeling mode.